1. Introduction
With a renewed awareness of the primacy of lexis within language related activities, the complex issue of learning and teaching vocabulary in English as an Additional Language (L2+) has inspired an increasingly extensive amount of research over the past two decades (Schmitt, 2008; Meara, 2002). Many questions remain, however, concerning how vocabulary is acquired, automaticity developed, and word knowledge processed.

The aim of this paper is to provide an overview of how explicit and incidental learning approaches are thought to inform vocabulary acquisition, and how through a combined integration, a complementary approach might be argued for and encouraged as a pedagogically appropriate option for learners of English at a post intermediate level.

The paper begins by providing a background outlining the inherent challenges and relevant issues of vocabulary acquisition upon which the eventual analysis and argument is based, and moves on to examine the reported effectiveness of learning vocabulary through a direct, explicit approach, and within an incidental, meaning focused framework. In this light, the effectiveness of extensive reading will be reviewed and the possible gains in vocabulary learning discussed. Additionally, noticing and its role in learning vocabulary will be examined and evaluated in view of its association with increasing opportunities for acquisition to take place.

Through an analysis of reported findings in which these elements are thought to converge to aid acquisition, an argument for a synthesis will be explored. This discussion will be based on current research and hypothesis, and related to previous findings in the area of vocabulary acquisition and extensive reading. Suggestions for pedagogical application will be implied, and the impact of learner strategies will be noted. Finally, a summary will be offered in support of an integrated approach, with focused noticing and learner engagement as crucial elements to be fostered within the creation of the necessary conditions for vocabulary acquisition to flourish.

2. Background
Let us begin by examining, in brief, some of the challenges facing learners in reference to vocabulary learning. In focusing on what a learner needs to know about a word, the first distinction made is usually the meaning-form connection. This might also be described as 'sight vocabulary', and is what is needed for automaticity to begin and continue to develop. The meaning-form connection, while adequate for recognition and general meaning, has its limitations, however, and at this initial receptive level, a number of further distinctions need to be made; for example, the word's sound/spelling relationship or likely patterns in which it can be found (Schmitt, 2008).

For recognition to be taken to the level of retrieval and production (Nation 2007: 7 in Schmitt ibid.) it is considered necessary that learners begin to make a number of contextual associations, an act which provides opportunities for deeper processing of the words encountered, allowing increased automaticity and acquisition to take place (Schmitt, ibid.). What is more, further knowledge regarding possible grammatical patterns, collocation, and constraints such as frequency and register need to be taken into account and learnt gradually (Schmitt, ibid.: 333-335). This underpins the incremental nature of vocabulary acquisition, which is thought to develop through extensive and regular exposure and the resulting incidental learning gains derived from the repeated encounters of vocabulary in context (Schmitt, 2005: 118; Nation, 2003: 238).

In brief, dependent on the personal goals of the language learner and his or her initial point of proficiency, what is necessary to be known about a word, and the number of words that need to be learnt and sustained, is a complex and challenging task. Learners of English, particularly at a post-intermediate level, are often heard to comment that what they lack above all is vocabulary. This is corroborated by research studies, in which the vocabulary sizes of learners often fall quite short of goals set, or the requirements necessary to operate in English comfortably (Laufer, 2000 in Schmitt, 2008: 332).